Reenforced concrete pipe



y 1932- c. F. BUENTE 1,869,183

REENFORCED CONCRETE PIPE Filed June 16, 1927 3 INVENTOR Patented July 26, 1932 UNITED STATES PATENT OFFICE CHARLES F. IBUENTE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO CONCRETE PRODUCTS COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- crete when the rods aretensioned.

SYLVANIA REENFORCED CONCRETE PIPE Application filed June 16,

This invention relates to reenforced pipe, and more particularly to a reenforced concrete pipe having the reenforcing advantageously disposed with particular reference to the load normally encountered in such pipes. To this end, the reenforcing is made of a geometrical shape different from that of the pipe itself, for example, a circular pipe may have an elliptical reenforcing cage therein, or an elliptical pipe may have a circular reenforcing.

Considering the load on a pipe buried in the earth, it will be seen that the concrete adjacent the inner surface will be in tension at the top and bottom of the pipe and in compression at the sides, while the concrete adjacent the outer surface will be in tension at the sides and in compression at the top and bottom. With a reenforcing of different configuration than the pipe, it. is possible to place steel in such relation to the inner and outer surfaces that it will take care of the tension loads in the most advantageous way.

In forming an elliptical reenforcing cage, I preferably utilize two generally semi-circular portions connected by short tangential elements, and form a truss across the tangential elements whereby the cage is maintained in the desired shape against the springing tendency of the reenforcing rod. The longitudinal elements of the cage are preferably welded to the circular elements and are so disposed that the stress imposed by the load normally encountered by the pipe is distributed over a large portion of the concrete, thereby obviating the possibility of the reenforcing rods to cut through the con- In the accompanying drawing illustrating certain preferred embodiments of my invention, 7 1

Figure 1 is a cross sectional view of'a circular pipe reenforced according to my invention;

Figure 2 is, a sectional view taken on the line II-II of Figure 1;

Figure 3 is an enlarged sectional viewof the trussed portion of the reenforcing; and

Figure 4 is a sectional view of an elliptical pipe reenforced according to my invention.

1927. Serial No. 199,195.

Referring to the illustrated embodiment, there is shown a generally circular pipe 2 having a reenforced steel cage therein. The cage comprises a helically wound rod or wire shaped on a suitable form so as to have substantially semi-circular portions 3 connected by short tangential portions 4, the tangential portions lyingat the top and bottom of the pipe. Longitudinal rods 5 are secured to the tangential elements 4, preferably by welding. Truss members 6 overlie the longitudinalmembers 5 and are secured to such members as well as to the semi-circular portions 3. Other longitudinal members 7 serve to stiffen the cage and sustain a portion of the longitudinal bending load on the pipe. The cage is preferably made by welding all intersections while the helically wound wire is still on the form. The wire usually employed has considerable spring and will tend to restore the cage to circular cross-section. This tendency, however, is overcome ifthe truss members 6 are welded in place while the cage is supported bythe form.

hen a pipe is-loaded with a concentratedload at the top thereof, the load moment and consequently the stress along thevertical axis in the steel, is approximately in the ratio of 16 to 9, as compared with the load moment and stress in the steel along the horizontal axis. If the pipe be uniformly loaded along the horizontal, these moments and stresses in the steel are equal. In actual practice, neither of these conditions ordinarily obtains, but the load near the central axis of the pipe is always greater than the load at the sides of the pipe. This results in the load moment and stress in the steel along the vertical axis AA being somewhat greater than the corresponding load momentand stress along the horizontal axis BB. The short circumferential trussing formed by the tangential portions 4 and the truss members 6 embracing the longitudinal elements 5 provide additional strength where the greater stresses are encountered.

i A load imposed on a reenforced concrete pipe sets up tension stresses in the steel which tend to straighten out the transverse reenforcing members. This results in a tendency of zontal axes.

the steel to shear its way through the concrete at the top and bottom portions of the pipe with the result that the pipe fails before the steel has reached this permissible maximum stress. By anchoring the circular reenforcement to a series of longitudinal members at the top and bottom of the pipe,the steel is firmly anchored in place and the load isso distributed that the effective stress in the steel may be greatly increased without danger of shearing the concrete.

In a straight concrete beam the adhesion between the concrete and steel is 'suflicient to prevent slipping of the concrete over the steel due to change in tensional stressin the steel. When the tensional stress reaches the :point where rupture of the concrete occurs, it results in a series of minute cracks which are harmless to the structure. In the .curved structure of a pipe the change in tension from its maximum along the vertical axis to the points of contraflexure is so great that the concrete slips on the steel with the formation, usually, of one large dangerous crack. An-

? choring the circular reenforcing to a series of longitudinal members prevents thisslipping and rupture in the concrete occurs by the formation of a number of smaller-less harmful cracks. This condition occurs only at-the points of maximum tension on-the inside of the pipe.

.As shown in Figure-2 the pipe .2 hasbell and spigot ends the bell 8 being provided taining cage is formed which will maintain its shape ina molding machine.

. Figure & illustrates an elliptical pipelO having a substantially circular reenforcing cage. therein. The cage is formed of a helically wound rod or wire shaped to form a cage having a substantially circular cross section.

The substantially circular convolutions 11 are connected by longitudinal rods 12 and 13 welded thereto. The longitudinal rods 12 are grouped together. at the top and bottom of the pipe to compensate for thedilference in load moments about the vertical and hori- The longitudinal rodslS stiffen the cage and also take a-portion of the bend- .ing load. The reenforcing is formed into a substantially unitary structure .by welding all points of intersection between the longitudinal members and the helically' wound rod whereby a stiff self-supporting cage is, formed capable of retaining its. shape during ;pouring and tampingoperations.

As indicated by dotted lines thepipe 10 is possible, without deflecting the reenforcing out of the shape to which it conforms within the body'of' the pipe which would interfere with tamping of the concrete.

Exterior indent-ions in the form o'fbeads 16 show the position of the reenforcing in the interiorof the pipe. l/Vhen laying the pipe, therefore,'itis easy to determine the correct position, sothat the interiorreenforcing. will be disposed .in the best position to take the load. WVhile-I have ShOWIl bBdS for ac complishlng this purpose, it willbeunderstood that any desired index maybe used totshow the correct position of the pipe with respect to'the applied-load.

WVhile I have illustrated and describedcertain preferred embodiments ofmy invention,

it will beunderstood that the invention 181 not limited thereto, but may be otherwise-embodied within the scope of the .fOllQWiIlg claims:

I claim:

1. A reenforced concretepipe having aa-re-w enforcing cage therein includinga plurality of longitudinal. reenforcing rods, the rods being disposed ingroupsat certain-portions of. the reenforcing whereby the pipe has increased, strength about: an axis thereof, and .2

means on the exterior ofthe pipe for indieating the correct position of the pipe when .in service.

,2. A reenforced concrete, pipe having trans verse reenforcing members, a plurality of grouped; longitudinal reenforcing ,rods, ;and truss members overlying the reenforcing rods, connected to the transverse members, .the longitudlnal rods being welded to the truss membersandto the transverse members.

.3. A rcenforcing cage for concrete pipe,

comprising a relatively springy member formed ,to non-circular contour, and truss means for resisting the spring-of the member tohold it to the desired contour.

4. A reenforcing cage for concrete pipe, comprisinga relatively sprlngy wire'wound to non-circularshape, and trusses secured-to the wire and effective. for holding it sub;

stantially to the shape in which it is wound. I 5. A reenforced concrete pipe having a re- -enforcing-cage therein, said cage comprising a truss applied clroumferentially to, saidcage,

the outer surface of the pipe havingan 11 n- 'dex forindicating the positionof saidtruss. '1

6. A reenforced concrete pipe-having agreenforcing cage therein. saidcage compris ng ;a continuous helix, each turn: thereof 5 having straightv portions and semi-circular. portions,

longitudinal. members connected. to said turns at the straight portions, and truss members overlying the longitudinal members connected at their ends to the semi-circular portions.

7. A reenforcing cage comprising a helix having a plurality of turns, truss members secured thereto at their ends, said truss members extending substantially parallel to said turns, and a longitudinal member lying between the truss members and the turns and secured thereto.

8. A reenforcing cage for concrete pipe including a helix having a plurality of turns including substantially straight portions, and

truss members overlying the straight portions of said turns, the truss members being effective for maintaining the cage in substantially elliptical shape against the spring of the reenforcing material.

In testimony whereof I have hereunto set my hand.

CHARLES F. BUENTE. 

